Translation of a walking transport vehicle can be achieved by way of displacing its platform relative to the legs that this platform uses to rest upon the travel surface, e.g. upon the ground surface. There is known, for example, a walking transport vehicle (U.S. Pat. No. 3,135,345) comprising a platform, two parallel rows of rectilinear guides mounted on the bottom side of the platform, extensible and retractable legs having their upper ends mounted within said guides, and means to shift the legs along the respective guides in a fore and aft direction. At each point in the forward travel of the transport vehicle, some of the legs are in the extended (working) position, resting upon the surface being travelled and stationary relative to this surface while moving aft along the respective guides relative to the platform (which moves forward by the same dint). At the same time the other legs are in the retracted (idle) position, out of contact with the travel surface and moving forward along the respective guides relative to the platform and also together with the platform at the same time. As a result, each of the legs performs a reciprocating movement relative to the platform in the process of translation or movement.
During the time interval which it takes the platform to move one step relative to the supporting legs in the working position, each of the "idle" legs must go up to move forward and then come down to be reliably positioned for operation upon the travel surface. The time required for this operation is relatively high. This is due to the process of extending the leg and positioning it for operation being rather slow, so that possible breakdown may be avoided. The result is a retarded translation of the transport vehicle, i.e., in its lower traveling speed.
As the platform is being translated, the idle legs move along with the platform. This being so, the platform must be immobilized when a leg comes down to contact the travel surface. Otherwise, the lower end of the leg would slide along the travel surface when the leg comes in contact with it. This is undesirable because it may lead to leg breakdown if, for instance, something on the travel surface happens to hinder the movement of the lower leg end along this surface. This leads to the necessity of arresting the movement of the transport after each step, thus decreasing the travelling speed still further. In this case, there is the inertia of the platform and the equipment mounted thereupon to be dealt with at the beginning and at the termination of each step. This results in lower walking vehicle efficiency, and more particularly, when heavily loaded massive platforms are used.
When using a transport vehicle of the type described above, a very serious problem is encountered in having the platform rotated for changing its travel direction. In the design as stated above this problem is handled by way of rotating the guides in which the upper ends of the legs are mounted. This arrangement, however, results in sliding of the lower ends of the leg over the travel surface during the platform rotation process. This may lead, as previously stated, to leg breakdown, especially when a heavily loaded platform is used. This impairs the reliability of movement of the transport vehicle when a turn has to be made.
Attempts at reducing leg sliding while turning lead to highly complicated transport vehicle constructions (Soviet Union Patent No. 821282; Soviet Union Patent No. 856890). Thus, Soviet Union Patent No. 856890 describes a design wherein flexible guides are used for preventing the legs from sliding while making a turn. These guides may be bent following segments of circles having a common center of curvature. However, this flexible guide design is of little use in practical applications, considering its complexity, poor reliability and low carrying capacity.
Speed increases in continuous translation of the platform of a walking transport vehicle can be achieved by displacing the legs relative to the platform with the aid of a band-type conveying device or conveyor means. There is known a transport vehicle of this type, namely, U.S. Pat. No. 3,522,859. This device is provided with two groups of extensible and retractable legs and two drive mechanisms mounted on the platform sides to provide for their movement. Each drive mechanism comprises a continuous band (chain) conveyor installed in a manner such that the two conveyor branches pass along the platform parallel to each other and to the conveyor branches of the other drive mechanism and are displaced vertically relative to each other, one being arranged above the other. The legs of one of the groups are mounted on the conveyor chain of one of the drive mechanisms while the legs of the other group are attached to the conveyor chain of the other drive mechanism. Running along the lower conveyor branch of each drive unit is a guide track which serves to support the upper ends of the legs while they are on the lower conveyor branch.
In the process of translation of the transport vehicle, some of the legs in each group are carried by the upper ("idle") branch of the respective conveyor. In this "idle" condition the legs are retracted. These legs move "forward" relative to the platform along with the conveyor chain and "forward" again along with the platform itself which is being translated relative to the travel surface. The other leg in each group are carried at the same time by the lower ("working") branch of the respective conveyor. These legs are in the working position, that is extended so that they contact the travel surface. The "working" legs are stationary relative to this surface while they move "backwards" relative to the platform, resulting in the platform itself moving "forward."
With the platform moving some distance forward, the rear-most "working" leg in each group, on the lower conveyor branch, is retracted, departing from the travel surface, and, as a result of translation along with the chain, passes over to the upper (idle) conveyor branch. At the same time, the foremost "idle" leg in each group, on the upper conveyor branch, passes over to the lower conveyor branch as a result of its movement with the chain. Having done so, the leg is extended and drops down to the travel surface.
As this leg is lowered down on to the travel surface, there is no movement by this leg along this surface, since all the other legs carried by the lower conveyor branch, as well as the corresponding part of the chain connecting them, are stationary relative to the travel surface.
In the process of further translation of the platform, the "idle" legs on each side of the platform pass over one by one on to the lower conveyor branch, to lower down to the surface. At the same time, the "working" legs pass over one by one after another over onto the upper conveyor branch. Thus, continuous translation of the platform is ensured in a rectilinear path parallel to the conveyor branches, without the legs sliding relative to the travel surface. This affords considerably higher translation speed for the transport vehicle.
The method proposed for turning the platform is by moving the conveyor chains at different speeds. However, this leads to the lower leg ends sliding over the travel surface. This results in, as previously mentioned, in leg breakdown, especially when using heavily loaded platforms.
There is known a walking transport vehicle wherein the conveyor branches of each leg drive mechanism are displaced horizontally rather than vertically (Soviet Union Patent No. 310012). In this transport vehicle, mounted to the platform are two closed guides passing over different sections of the bottom surface of the platform and each having two sections connected in series passing rectilinearly in parallel to each other and to the sections of the other guide. The first guide mounts the upper ends of the first group of legs, the second guide correspondingly mounts the upper leg ends of the second group of legs. The transport vehicle also contains a drive mechanism for moving the first group of legs along the first guide and a drive mechanism for moving the second group of legs along the second guide. Each leg drive mechanism comprises a continuous band conveyor with conveying branches passing respectively, along the corresponding guide sections, and means to connect the upper ends of the legs of the corresponding group with the conveyor band.
In the process of translation of this transport vehicle, the legs moving along one of the parallel sections of each guide are in the idle position while the legs moving (relative to the platform, not the travel surface) along the other section of this guide are in the working position. They rest upon the travel surface and remain stationary relative to this surface until they pass, along with the chain, onto the "idle" guide section.
This walking transport vehicle design, just as the transport vehicle construction with the conveyor units, as previously described, will assure a relatively fast and continuous translation of the platform. But these designs will not permit the turning of the platform without the lower ends of the legs sliding over the travel surface, thereby reducing the reliability of movement of the transport vehicle while making a turn.